Problem: Emily ate 3 slices of pizza. Tiffany ate 2 slices. If Emily ate $\dfrac{3}{6}$ of the pizza, what fraction of the pizza is remaining?
If 3 slices represent $\dfrac{3}{6}$ of the pizza, there must have been a total of 6 slices. $\text{fraction of pizza remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 5 slices, which leaves 1 out of 6 slices remaining. There is $\dfrac{1}{6}$ of the pizza remaining.